In the field of cryopreservation of biological samples, there is an increasing need for storing large numbers of samples at a cryopreservation temperature, like e.g. the temperature of liquid nitrogen or vapour of liquid nitrogen. The samples are stored in thermally insulated containers (so-called cryo-tanks).
Typically, the samples are deposited in combination with associated sample data including an identification of the samples and optionally further specific information, like e.g. properties of the sample's donor or data concerning a previous processing of the samples. In DE 100 60 889 A1, the combined arrangement of sample receptacles and sample memories in the cryo-tank has been proposed for ensuring that the correspondence of the sample and the assigned sample data is kept during the cryopreservation. The sample receptacles and memories are arranged on a common carrier or board, which includes a processor circuit for controlling the sample memories. All sample receptacles and memories are connected in parallel with the processor circuit.
For accessing to the sample data from outside the cryo-tank, a communication channel is required for connecting the sample memories with e.g. a host computer. If a plurality of sample receptacle and memory boards is arranged in the cryo-tank, particular demands are made on the communication channel as the processor circuits of the boards create a complex structure requiring a large number of wire-connections. The technique disclosed in DE 100 60 889 A1 has a restriction as it does not disclose an effective management of the data access to the plurality of sample receptacle and memory boards.
Wireless communication channels using transponder technology have been proposed in DE 102 02 304 A1 and DE 299 12 346 U1. The transponder technology has advantages in terms of avoiding any thermal bridge trough a wall of the cryo-tank. However, there are limitations if a large number of samples and sample data are to be handled. With increasing storing density, RFID transponders may interfere each other.
Another wireless communication channel for general applications has been developed with the WLAN technology, which, however, requires that all available clients are powered for an access from a host computer. Accordingly, the WLAN technology would have disadvantages if used for cryopreservation purposes as powered clients would provide heat sources in the cryo-tank.
F. R. Ihmig et al. (“Cryogenics” vol. 46, 2006, p. 312 to 320) have proposed a wire-bound communication channel based on a multiplexer system as schematically illustrated in FIG. 6. The cryopreservation apparatus 200′ comprises a multi sample module 20′ including eight sample data memory cards 21′ (FLASH memories), a module control device 30′ for controlling an access to the memory cards accommodated by the multi sample module 20′ and a host computer 70′. The components 20′ and 30′ are arranged in the cryo-tank 60′ at cryopreservation temperature, while the host computer 70′ is positioned at room temperature. The module control device 30′ comprises an address logic 31′ and an analog switch circuit 32′. The host computer 70′ is connected via first and second data interfaces 41a′, 41b′ with the address logic 31′ and the analog switch circuit 32′, resp.
With an increasing number of samples and sample data, the conventional multiplexer system requires an increasing number of wire connections from the host computer 70′ into the cryo-tank 60′. As an example, the conventional eight channel design requires 50 pin connections of the second data interfaces 41b′. In practice, even more, e.g. more than 200 wires would be necessary for connecting all sample data memory cards 21′ with the host computer 70′. The increasing number of wire connections create a disadvantageous heat bridge having a negative effect on the temperature control of the cryo-tank. Another problem of the conventional multiplexer system is given by the fact that all sample data memory cards 21′ have to be activated for accessing to any sample data. Activating all sample data memory cards 21′ requires an essential power consumption and a corresponding generation of heat inside the cryo-tank. Accordingly, a further cooling efficiency of the conventional cryopreservation apparatus 200′ can be limited. If the conventional multi sample module 20′ is to be removed from the cryo-tank, another disadvantage arises due to the complex structure and large number of wire-connections of the multiplex system.